Fig. 4. Multiple alignment of the deduced amino acid sequence of the serine protease domain of S. haematocheir OHSS with those of known serine proteases of six species. Regions of high homology across all species are highlighted in black (100–90%); regions with less homology are highlighted in gray (>80%) and purple (>60%). The numbering of amino acids corresponds to the original sequences in each animal. Information for comparison: chymotrypsin of Penaeus vanameii (database accession number S29239); trypsin of Paralithodes camtschaticus (AF461036); proclotting enzyme (procl.) of Tachypleus tridentatus (P21902); defensin of Pacifastacus leniusculus (AJ007668.1); human hepsin (P05981); human matriptase (Q9Y5Y6). Residues in the catalytic triad (His-293, Asp-346 and Ser-441) are indicated by an asterisk. Residues in the substrate pocket (Asp-435, Gly-463 and Gly-473) are indicated by diamonds. Six conservative cysteines needed to form three intramolecular disulfide bonds are likely pairings as follows: Cys278–Cys294, Cys411–Cys426, and Cys437–Cys466. The disulfide bond Cys246–Cys366 (the cysteines are boxed) is observed in two-chain serine proteases, but not in trypsin and chymotrypsin.